Field of the Invention
The present invention relates to a working vehicle having a DPF and an SCR as an exhaust gas cleaning device.
Description of the Related Art
A Diesel Particulate Filter (to be referred to shortly as “DPF” in this disclosure) and a Selective Catalytic Reduction (to be referred to shortly as “SCR” in this disclosure) for cleaning exhaust gas from an engine are known from e.g. Japanese Unexamined Patent Application Publication No. 2009-167806 (Patent Document 1). In this document, there is described an exhaust gas cleaning device for an engine, consisting of a DPF and an SCR arranged in juxtaposition, a connecting pipe connecting one side end of the DPF and the other side end of the SCR, and a reducing agent supplying nozzle disposed upstream of the connecting pipe.
With the exhaust gas cleaning device configured as above, exhaust gas from an engine is fed to the DPF and PM (particulate matters) contained in the exhaust gas are collected by the DPF. The exhaust gas past the DPF is then fed to the SCR via the connecting pipe. In the course of this, an amount of reducing agent (e.g. ammonia) is injected into the connecting pipe from the reducing agent supplying nozzle to be mixed with the exhaust gas. With this, inside the SCR, there occurs a chemical reaction between the reducing agent and nitrogen oxides contained in the exhaust gas, whereby the nitrogen oxides are reduced to nitrogen, a harmless substance, and water. According to the technique described in Patent Document 1, mixing between the reducing agent and exhaust gas is promoted by securing a long total length for the connecting pipe.
However, when an exhaust gas cleaning gas consisting of a DPF and an SCR is applied to a working vehicle such as a tractor, following problems occur.
Normally, an engine of a working vehicle is housed in an engine room covered by a hood and having only a limited space. For this reason, it is contemplated to dispose the exhaust gas cleaning device outside the engine hood. Yet, if consideration is given to possibility of interference between such exhaust gas cleaning device disposed outside the hood and various working implements (e.g. a front loader, etc.) mounted on the working vehicle, a location allowing mounting of such working implement(s) will necessarily be limited and readiness in mounting the working implement too will be deteriorated. For allowing smooth mounting of the implement, a significant design change (e.g. change of the wheel base, etc.) will become necessary in the working vehicle per se.
Thus, it becomes necessary to enlarge the hood for allowing accommodation of the exhaust gas cleaning device within a resultantly enlarged engine room. However, this enlargement of the engine room, i.e. enlargement of the hood, results in blocking of operator's view by the hood, which in turn can lead to deterioration in the operator's visibility and operability of the working vehicle.